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Mains Harmonic in the 30W offline LED driver

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treez

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Sorry i cant find my previous similar post on this.
The attached is the mains iin and vin of 30W offline led driver.
Power factor is 0.96.
Mains harmonic number 2 is bad though.
Why is this kind of driver victimised against, when it is so efficient?
 

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  • Schematic _30W Buck PFC LED.jpg
    Schematic _30W Buck PFC LED.jpg
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There is no second harmonic in the current waveform, quite unlikely for a converter with bridge rectifier. You see odd harmonics only (3,5, 7...).
 
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Please can anyone give a reminder of the maximum allowable THD for a LED lamp of 30W+?
(in Europe and USA)

i dont have the EN61000-3-2 to hand and the web doesnt have it..

https://www.google.co.uk/#q=epsma+mains+harmonics

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There is no second harmonic in the current waveform, quite unlikely for a converter with bridge rectifier. You see odd harmonics only (3,5, 7...).
Click to expand...
i admit its very very little, and should be deemed insignificant, but the regs are very harsh on Harmonic nnumber 2.
If you take the FFT you can see energy at 100Hz, the second mains harmonic
 

I can't make a measurement because you didn't post a simulation circuit.

Again, stationary solution of bridge rectifier circuit won't have 2nd harmonic.
 
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This is reLated to the above, please may i place it here?

We know that offline LED lighting from 25W to 75W needs to be power factor corrected to at least 0.9

Though can you confirm that the mains harmonic limits are relaxed for this power level of lighting?....ie the limit is 25% for THD for offline lighting products between 25W and 75W?

...in other words, for lighting products between 25W and 75W, even if you fail on some mains harmonic currents, then as long as your overall THD is less than 25%, than you pass European regulations on mains harmonics?
 

Do you know what is the problem with mains harmonics?...i take it that they are too low in frequency to be attenuated by mains line inductance, and so they propagate and cause core loss heating in supply system transformers...is this correct?
 

treez said:
i admit its very very little, and should be deemed insignificant, but the regs are very harsh on Harmonic nnumber 2.
If you take the FFT you can see energy at 100Hz, the second mains harmonic
Click to expand...
I think I know why do you see that harmonic there which in reality it does not exist.
If I am correct, it is simply a simulation error.

In order to check that, simulate an integer number of cycles of the current waveform and then apply the FFT. In post #1, you have simulated 1.5 cycles (30 ms) of the current waveform. Simulate either 1 (20 ms) or 2 (40 ms) or 3 (60 ms) etc.. but it has to be an integer number.

If I am correct, tell me and I will give further explanation. If you still see the 100 Hz harmonic, then I do not know.
 
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Hello,
This is related in some way to the above, so please may i post it here?....

I appreciate that for Europe/UK, the regulatory bodies test SMPS’s for mains harmonics at 10V intervals between 195VAC and 265VAC……But is it only the result at 240VAC that determines if it’s a pass or fail?
 

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